/Engine/Source/Developer/TargetPlatform/Public/Interfaces/IAudioFormat.h
This function is, as far as I can tell, unused.
The size of the compressed audio, or 0 on failure.
int32 Recompress ( [FName](API\Runtime\Core\UObject\FName) Format, const [TArray](API\Runtime\Core\Containers\TArray)< uint8 > & SrcBuffer, [FSoundQualityInfo](API\Developer\TargetPlatform\Interfaces\FSoundQualityInfo) & QualityInfo, [TArray](API\Runtime\Core\Containers\TArray)< uint8 > & OutBuffer ) const